1. Field of the Invention
The present invention relates to a numerical control data dividing and editing apparatus which can rapidly edit numerical control data for controlling operation of a numerical control machine tool.
2. Description of the Prior Art
In recent years, many composite machine tools such as machining centers and turning centers have been introduced into machine tool workshops. These machine tools contribute to an improvement of efficiency in productivity because of their many functions which prior art single-function machine tools did not have.
FIG. 1 shows a perspective view of such a machine tool workshop which comprises three numerical control (NC) machine tools M.sub.1 -M.sub.3, numerical control units 1-3 associated with respective NC machine tools, an automated cart 4, a stocker 5 and a control computer 6. The NC machine tools M.sub.1 -M.sub.3 have automatic tool changers (ATC) 7-9, respectively, which automatically exchange tools in accordance with instructions from the associated NC units 1-3, and automatic pallet changers (APC) 11-13 which automatically exchange pallets 10 on which workpieces are mounted.
An outline of machining operation in the machine tool workshop is now explained. A workpiece mounted on the stocker 5 is conveyed to the machine (M.sub.1 -M.sub.3) by which it is to be machined, by the automated cart 4 and set to the APC (11-13). When the machining operation of the workpiece being machined by the machines (M.sub.1 -M.sub.3) is completed, the APC (11-13) is automatically moved so that the conveyed workpiece is set to the machine and the NC data necessary for that workpiece is supplied from the control computer 6 and the machining operation starts. The workpiece machined by the machine is returned to the stocker 5 by the automated cart 4. In this manner, the workpieces mounted on the stocker 5 are sequentially machined.
On the other hand, in editing the NC data, automatic program languages such as APT (automatically programmed tools) and EXAPT (extended subset of APT) are used. In this system, a part programmer writes a part program in accordance with a design drawing, which program is then executed by an automatic programming apparatus to generate necessary NC data. In writing the part program, the programmer assumes a particular machine tool for machining particular parts and a particular NC unit.
Since the NC machine tools M.sub.1 -M.sub.3 can carry out various machining operations, several alternatives may exist for the machine tool used and the sequence of operations thereof to machine a given workpiece. In order to attain an effective operation of the workshop, it is desirable to instantly allot proper jobs depending on conditions of the field such as a variation of types of workpieces, presence of an urgently required workpiece, overload or underload conditions, failure of machine tool and breakage of a tool.
In the prior art NC data editing system, however, when the machining steps or the machine tools used are changed, the part program must be rewritten in order to get the necessary NC data. This takes a long time.